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What is DOM What is DOM
DOM is Document Object Model Document Object Abbreviation for model. According to the W3C DOM specification (http://www.w3.org/DOM/), DOM is a browser-, platform-, and language-independent interface that allows you to access other standard components of the page. Simply understood, DOM resolves the conflict between Netscape's Javascript and Microsoft's Jscript, giving web designers and developers a standard way to access data, scripts, and presentation layer objects in their sites.
DOM (Document Object Model)
DOM is the abbreviation of Document Object Model. According to the W3C DOM specification (http://www.w3.org/DOM/), DOM is a browser-, platform-, and language-independent interface that allows you to access other standard components of the page. Simply understood, DOM resolves the conflict between Netscape's Javascript and Microsoft's Jscript, giving web designers and developers a standard way to access data, scripts, and presentation layer objects in their sites.
DOM is a collection of nodes or information fragments organized in a hierarchical structure. This hierarchy allows developers to navigate the tree looking for specific information. Analyzing this structure typically requires loading the entire document and constructing the hierarchy before any work can be done. Because it is based on information hierarchy, the DOM is considered tree-based or object-based.
For particularly large documents, parsing and loading the entire document can be slow and resource-intensive, so it is better to use other means to process such data. These event-based models, such as Simple API for XML (SAX), are suitable for processing data streams, that is, processing data sequentially as it flows. The event-based API eliminates the need to construct the tree in memory, but does not allow developers to actually change the data in the original document.
Models such as SAX will parse the entire XML document sequentially from beginning to end. When encountering the beginning or end of a node, an event will be generated. Programmers can register event handling functions to process each node.
On the other hand, DOM also provides an API that allows developers to add, edit, move or delete nodes anywhere in the tree, thereby creating a reference program. This model is based on a tree data structure, which must load the entire document or at least a well-structured document fragment before use
A parser is a software application designed to analyze documents (here XML files), and do something specific to that message. In an event-based API like SAX, the parser will send events to some kind of listener. In a tree-based API such as DOM, the parser will construct a data tree in memory.
DOM as API
Starting from DOM Level 1, the DOM API contains interfaces for representing all the different types of information that can be found in XML documents. It also contains the methods and properties necessary to use these objects.
Level 1 includes support for XML 1.0 and HTML, and each HTML element is represented as an interface. It includes methods for adding, editing, moving, and reading the information contained in nodes, and more. However, it does not include support for XML Namespaces, which provide the ability to segment information in a document.
DOM Level 2 adds namespace support. Level 2 extends Level 1 by allowing developers to detect and use namespace information that may apply to a node. Level 2 also adds several new modules to support cascading style sheets, events, and enhanced tree operations.
Currently in the final stages of finalization, DOM Level 3 includes better support for creating Document objects (previous versions left this task to the implementation, making creating universal applications difficult), enhanced namespace support, and the ability to New modules that handle document loading and saving, validation, and XPath; XPath is a means of selecting nodes in XSL Transformation and other XML technologies.
The modularity of the DOM means that as a developer, you must know whether the features you want to use are supported by the DOM implementation you are using.
Determining feature availability
The modular nature of DOM recommendations allows implementers to pick and choose which parts to include in the product, so before using a specific feature, it may be necessary to first determine whether the feature is available. This tutorial only uses the DOM Level 2 Core API, but when starting your own projects it's helpful to know how you can detect features.
One of the interfaces defined in DOM is DOMImplementation. By using the hasFeature() method, you can determine whether a specific feature is supported. There is no standard way to create a DOMImplementation in DOM Level 2, but the following code shows how to use hasFeature() to determine whether a DOM Level 2 stylesheet module is supported in a Java application.
XML file parsing method: DOM, which is in the form of a document, reads all the contents of the xml file into the memory at one time. You can use the node value in the content
sax method: Event
To put it bluntly, DOM is a concrete structural model that makes the content look clearer
Document Object Model: an object-based development model for parsing documents
What is dom, what is dom What's the meaning?
DOM is the abbreviation of Document Object Model, which is the document object model. W3C launched the DOM level 2 specification on November 13, 2000. DOM is a programming interface specification for HTML and XML documents. It is independent of platform and language, so it can be implemented in various languages and on various platforms.
This model defines the in-memory document structure of HTML and XML files, and provides access and storage methods for HTML and XML files. Using DOM specifications, you can realize mutual conversion between DOM documents and XML, and perform traversal or other operations on the contents of the corresponding DOM documents. If you want to freely manipulate XML files, you must use the DOM specification.
Simply put, the principle of DOM is to logically build a tree model for the XML document by parsing the XML document. The nodes of the tree are objects. We can manipulate the content in the XML document by accessing these objects.
Advantages and Disadvantages of DOM
The advantages of DOM are mainly: ease of use. When using DOM, all XML document information will be stored in memory and traversed Simple, supports XPath, enhances ease of use.
The main disadvantages of DOM are: low efficiency, slow parsing speed, high memory usage, and almost impossible to use for large files. In addition, low efficiency is also reflected in a large amount of time consumption, because when using DOM for parsing, an object will be created for each element, attribute, processing-instrUCtion and comment of the document, which requires the creation of a large number of objects used in the DOM mechanism. and destruction will undoubtedly affect its efficiency.
DOM is the abbreviation of Document Object Model, which is the document object model. W3C launched the DOM level 2 specification on November 13, 2000. DOM is a programming interface specification for HTML and XML documents. It is independent of platform and language, so it can be implemented in various languages and on various platforms.
This model defines the in-memory document structure of HTML and XML files, and provides access and storage methods for HTML and XML files. Using DOM specifications, you can realize mutual conversion between DOM documents and XML, and perform traversal or other operations on the contents of the corresponding DOM documents. If you want to freely manipulate XML files, you must use the DOM specification.
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